This invention relates to a high speed rotational supporting device for a disk such as a floppy disk.
In a process of producing, for example, floppy disks, an operation for working a surface of a disk or for contacting an inspection tool with a disk is carried out while the disk is being rotated during a polishing or inspection step of the disk. In achieving such operations, increase of the rotational speed is desired in order to improve the working efficiency.
Referring to FIG. 1 which illustrates a typical one of conventional high speed rotational supporting devices for disks, a movable rotary shaft 2 is mounted in coaxial relationship and for movement into and out of engagement with a stationary rotational shaft 1 such that a floppy disk 3 is clamped between opposing end faces of the rotational shafts 1 and 2. The stationary rotary shaft 1 is supported for rotation on a housing 4 by means of bearings 4a and is driven by a belt 7 extending between a pulley 5 thereon and another pulley 6 of a prime mover. Meanwhile, the movable rotary shaft 2 is supported for rotation and also for sliding movement by means of a housing 8 and is moved up and down by an actuating lever 9. A pressing up mechanism 11 is provided for pressing a disk 3 against an operating head 10 such as a magnetic head or a polishing roll.
In the device having such a construction as described above, if a floppy disk 3 clamped between the rotational shafts 1 and 2 is rotated at a high speed, it may make eccentric rotation and thus produce vibrations since a slightest dislocation between the axes of the shafts 1 and 2 cannot be avoided. As a result, there may be such defects as deviations in working accuracy, appearance of friction between an end face of either or each shaft and a contact face of the disk, and damage to bearings at supporting portions for the shafts.